Bailing devices

ABSTRACT

A bailing device for a dinghy comprises a duct having a convergent inlet section, a divergent outlet section, and a low pressure zone. A passage extends between the low pressure zone and the interior of the hull of the dinghy. The device projects downwardly from the hull with the axis of the duct extending fore and aft of the hull. Flow of water thru the duct during movement of the dinghy creates a pressure drop in the low pressure zone whereby water is drawn thru the passage from the hull.

United States Patent Brazier BAILING DEVICES [76] Inventor: Peter H.Brazier, 49 Richmond Way, Fetcham, Surrey, England [22] Filed: July 19,1974 [21] Appl. No.: 490,123

[52] US. Cl. 114/185 [51] Int. Cl. B63B 13/00 [58] Field of Search114/183 R, 183 A, 184,

[56] References Cited UNTTED STATES PATENTS 2,138,368 ll/l938 Briant114/185 2,479,783 8/1949 Sawyer 114/185 3,027,861 4/1962 Whitehead.....114/185 3,460,503 8/1969 Chalmers ll4/l85 Primary Examiner-Trygve M.Blix Assistant ExaminerStuart M. Goldstein Attorney, Agent, orFirmWolfe, Hubbard, Leydig, Voit & Osann, Ltd.

[57] ABSTRACT A bailing device for a dinghy comprises a duct having aconvergent inlet section, a divergent outlet section, and a low pressurezone. A passage extends between the low pressure zone and the interiorof the hull of the dinghy. The device projects downwardly from the hullwith the axis of the duct extending fore and aft of the hull. Flow ofwater thru the duct during movement of the dinghy creates a pressuredrop in the low pressure zone whereby water is drawn thru the passagefrom the hull.

1 Claim, 4 Drawing Figures US. Patent 0a. 14, 1975 FIG. 2.

F/GJ.

BAILING DEVICES BACKGROUND OF THE INVENTION 1. Field of the InventionThe present invention relates to pumping devices and more particularlyto bailing devices for use with sailing dinghies and other smallvessels.

2. Description of the Prior Art One previously proposed bailing devicefor use with dinghies, particularly racing dinghies, comprises arearwarly inclined flap depending from the hull of the dinghy with apassage extending from the trailing edge of the flap to the interior ofthe hull. During movement of the dinghy, the pressure-drop created asthe water flows along the surface of the flap causes water to bewithdrawn from the interior of the hull through the passage. As will beapparent, the bailing device will only operate in this manner when thepressure-drop (expressed as a head of water) across the flap is inexcess of the draught of the dinghy, that is when the speed of thedinghy exceeds a predetermined minimum speed. In the previously proposeddevice, this minimum speed is relatively high. Further, the flap exertsa relatively high drag.

SUMMARY OF THE INVENTION According to the present invention, there isprovided a bailing device for a dinghy or other vessel comprising a ducthaving a convergent inlet section and a divergent outlet section, meansfor mounting the duct on the hull of the vessel such that the duct liesin the water, with the axis of the duct lying fore and aft of the hull,and means defining a passage arranged to extend between the interior ofthe hull and a low pressure zone within the duct.

Further according to the present invention, there is provided a vesselhaving a bailing device mounted on its hull, the bailing devicecomprising a duct extending longitudinally of the hull, the duct havinga convergent inlet section, a divergent outlet section, and a throatsection between the inlet and outlet sections, the inlet section beinglocated in front of the outlet section in the normal direction ofmovement of the vessel, and a passage extending between the interior ofthe hull and the interior of the duct at or adjacent the throat section.

BRIEF DESCRIPTION OF THE DRAWING DESCRIPTION OF THE PREFERREDEMBODIMENTS As shown in the drawings, the bailing device comprises arectangular-sectioned duct defined by a pair of opposed, parallel sidewalls or plates 1, and a bottom.

member 2. A member 3 is mounted in the front end portion ofthe ductbetween the side plates 1; the shape of the lower face of member 3 issuch that'the passage defined between member 3, member 2 and the sideplates 1 is a convergent flow passage. The lower edge of the member 3 inthe direction at right angles to the side plates, is parallel to, andspaced from, the bottom member 2. Although as described above, the ductis of rectangular section, it can alternatively be of axisymmetricalform.

A member 4 is mounted within the duct behind the member 3 and has aconvex leading edge portion which is spaced from the rear surface of themember 3, and a plane under surface which faces the upper surface of themember 2 and which is inclined with respect to the member 2.

The member 3 and the member 4 define together with the lower portions ofthe side plates 1 and the bottom member 2, a passage having a convergentsection 5, a mixing section 6, and a divergent section 7. As can be seenfrom FIG. 1, the convergent section 5 lies beneath the curved portion ofthe member 3, the mixing section 6 lies beneath the convex leading edgeportion of the member 4, and the divergent section 7 lies beneath theinclined under surface of the member 4. The passage has an inlet 8 andan outlet 9. The members 2,3 and 4 can be formed from a plasticsmaterial and the other components of the device can be formed fromstainless steel. The bailing device is mounted on the hull 10 of adinghy such that the passage lies beneath the underside of the hull withthe inlet 8 and the outlet 9 lying respectively fore and aft along thelongitudinal axis of the hull 10. A passage 11 which providescommunication between the mixing section 6 and the interior ofthe hull10 is defined between the member 3 and the leading edge portion of themember 4. Preferably, in the operating position of the device the bottommember 2 is inclined downwardly relatively to the axis of the hull, in arearwards direction by a relatively small angle, for example up to about5. During forwards movement of the dinghy, water enters the inlet 8 andis accelerated in the convergent section 5; this flow of water will betermed the primary flow. The acceleration causes a decrease in the fluidpressure so that the pressure in the section adjacent the trailing edgeportion of the member 3 which constitutes a throat section 12 is lessthan the pressure at the inlet 8. If the pressure of water within thehull is less than that at the throat section 12, the water within thehull will be drawn from the hull through the passage 11; this flow ofwater will be termed the secondary flow. The secondary flow is mixedwith the primary flow in the mixing section 6 and the combined flowpasses through the divergent section 7; the combined flow is deceleratedwhich results in recovery of the pressure, the flow being dischargedthrough the outlet 9.

The flow area at the throat section 12 determines the pressure at thethroat section 12 and hence the suction pressure. As the area at thethroat section 12 is decreased, the acceleration of the primary flow isincreased and the pressure at the throat section 12 is decreased.However, with increasing flow velocities and a decreasing distancebetween the member 3 and the bottom member 2, the friction lossesincrease. As a result, there is an optimum ratio between the area of thethroat section 12 and the area of the inlet 8, the ratio being betweenabout 0.3 and 0.5. With this optimum ratio, the bailing device iseffective at relatively low speeds or with a dinghy of considerabledraught.

As will be apparent however, it is also desirable that the volumetricpumping capacity of the bailing device be relatively high. Thischaracteristic is influenced by the shape of the mixing section 6 and ofthe passage 11. For this purpose the passage 11 should be relativelylarge and should discharge the secondary flow in a direction parallel tothe primary flow for which purpose the downstream end portion of thepassage 11 extends parallel to the axis ofthe duct. This arrangementresults in flow losses which increase the suction pressure. The deviceshown in FIG. 1 is a compromise between the two requirements.

The mixing of the primary and secondary flows occurs in the mixingsection 6 in which the low velocity secondary flow is accelerated by thehigh velocity primary flow issuing from the throat section 12. Themixing section should be of such a length that the secondary flow hasbeen accelerated at least to some degree before entering the divergentsection 7. The mixing section can, however, be omitted ifit is necessaryto reduce the axial length of the device.

The divergent section 7 is, in effect, a conventional diffuser.Generally the angle of divergence should be less than about sinceotherwise the flow will spearate from the walls of the passage and therequired pressure recovery will not be achieved.

The difference between the pressure at the inlet 8 and the throatsection 12 is termed the suction head. As the pressure at the throatsection 12 decreases the suction head increased.

In the bailing device, the suction head is proportional to the square ofthe velocity of the dinghy. Therefore, for a dinghy of given draughtthere is a minimum speed at which the device can operate. Below thisspeed the pressure at the throat section 12 is greater than the pressureat the inlet portion 22 of the passage 11, in this event water will tendto flow into the hull 10. To prevent such return flow, a non-returnvalve can be fitted in the passage 11. A suitable non-return valve cancomprise a deformable sleeve supported at its upstream end portion, thedownstream end portion of the sleeve being free and opening during flowfrom the inlet secber 19 which is attached to the top of the device, sopulling the device upwards through the aperture in the flange 13.Rotation of the lever 16 also initially extends the spring 18 soincreasing its tension. When the device is about half way up the spring18 exerts an anticlockwise force on the lever 16 so causing the lever totion 22 to the throat section 12; the downstream end a portion of thesleeve closes upon flow in the reverse direction (whereby to preventsuch flow). However due to the good low speed characteristics of thedevice, a non-return valve is not essential and has not been shown.

The device can be permanently mounted on the underside of the bull orcan be retractable to enable the dinghy to be launched from a sandy orother shore. A retractable mounting will now be described.

In the operating or open position, the duct defined by the side plates 1and the bottom member 2 projects through an aperture in a flange 13which is mounted on the hull 10. A neoprene or other gasket 14 makes aseal between the flange l3 and a lip 15 which extends around the topportion of the assembly formed by the member 3 and 4. The device is heldin this operating position by a lever 16 which is pivotal between twostop positions. This lever 16 pivots in side brackets 17 and presses onthe top of member 4. A downwards force on the lever 16 is maintained bya spring 18 which may be of rubber shockcord or other material.

To retract the device the lever 16 is pulled upwards and anticlockwisefrom one stop position. This has two effects. The lever 16 exerts anupward force on a memrotate rapidly anti-clockwise into its other stopposition so fully retracting the device. In this retracted position alip 20 which extends around the lower member 2 seals on a neoprene orother gasket 21 which is bonded to the flange 13. The lever 16 can thenbe rotated anticlockwise by hand to the position shown in FIG. 3. Thislocks the device in the retracted position and exerts a compressionforce between the lip 20 and the gasket 21 sufficient to ensure a leakfree joint. In the locked position the device can only be lowered to theoperating position by rotating the lever 16 clockwise. Once started,however, the device springs to the down or operating position. Oneadvantage of the spring loaded lever 16 is that the device is either inthe retracted or the operating position. It will not stay in anintermediate position where water can leak into the dinghy.

In its normal operating position as shown in FIGS. 1 and 2, the axis ofthe primary flow passage extends generally parallel to the plane of theflange l3 and hull 10 and thus to the general direction of movement ofthe dinghy; the pressure difference between the inlet 8 and the outlet 9is very small in this position. This pressure difference is determinedby the disturbance to the external flow around the device. Due to thissmall pressure difference the drag exerted by the device is low.

In a modified form of the device (not shown) the bottom plate is omittedand the convergent-divergent passage is formed by two hollow, shaped,side members which extend vertically downwards. The secondary flowenters via a vertical slot in each side member, the slots being locatedat the throat section of the passage. A flow passage extends from theinterior of the hull to the inside of the side member.

The omission of the bottom plate does not adversely affect theperformance of the device to any significant degree and will beadvantageous in situations where fouling is likely to occur due toaccumulations of weeds and other matter in the water. In this case whenthe device is withdrawn into the hull so that the lower edges are flushwith the underside of the hull, weeds or other matter whichhas collectedon the device will be pushed from the device.

The bailing device particularly described is more effective at lowspeeds than the aforesaid previously proposed bailing device. Theminimum operating speed of the device for a dinghy of draught 4 inchesis about 1% knots compared with about 3 knots for the previouslyproposed device and the device has negligible drag in its normaloperating position; at speed of 5 knots this represents a reduction indrag of about 15 lb. force.

What is claimed is:

1. In a bailing device for a vessel,

a duct assembly defining a duct having a convergent inlet section, adivergent outlet section, and an intermediate low pressure zone, saidduct assembly being located within an aperture in the underside of thehull of the vessel,

a mounting assembly mounting the duct assembly for movement between anoperative position in which the duct is located outwardly of the hullwith the axis of the duct lying fore and aft of the hull and an itsinoperative position, movement of the lever means between its stoppositions serving to move the duct assembly between its operative andinoperative positions rectilinearly in a direction transverse to theaxis of the duct assembly, and passage means defined within the ductassembly and extending between the low pressure zone and the interior ofthe hull.

l l l

1. In a bailing device for a vessel, a duct assembly defining a ducthaving a convergent inlet section, a divergent outlet section, and anintermediate low pressure zone, said duct assembly being located withinan aperture in the underside of the hull of the vessel, a mountingassembly mounting the duct assembly for movement between an operativeposition in which the duct is located outwardly of the hull with theaxis of the duct lying fore and aft of the hull and an inoperativeposition in which the duct is retracted within the hull, said mountingassembly comprising mounting means secured in the interior of the hull,and manually operable pivotal lever means linked to the mounting meansand the duct assembly, said lever means being located in the interior ofthe hull and being pivotal from a first stop position in which the ductassembly is in its operative position and a second stop position inwhich the duct assembly is in its inoperative position, movement of thelever means between its stop positions serving to move the duct assemblybetween its operative and inoperative positions rectilinearly in adirection transverse to the axis of the duct assembly, and passage meansdefined within the duct assembly and extending between the low pressurezone and the interior of the hull.